Papers

SAE 970625

Effects of Injection Timing on Air-Fuel Mixing in a Direct-Injection Spark-Ignition Engine

By: Zhiyu Han, Rolf D. Reitz, J. Yang, R. W. Anderson

Abstracts

Multidimensional modeling is used to study air-fuel mixing in a direct-injection spark-ignition engine. Emphasis is placed on the effects of the
start of fuel injection on gas/spray interactions, wall wetting, fuel vaporization rate and air-fuel ratio distributions in this paper. It was found
that the in-cylinder gas/spray interactions vary with fuel injection timing which directly impacts spray characteristics such as tip penetration
and spray/wall impingement and air-fuel mixing. It was also found that, compared with a non-spray case, the mixture temperature at the end of the
compression stroke decreases substantially in spray cases due to in-cylinder fuel vaporization. The computed trapped-mass and total heat-gain from
the cylinder walls during the induction and compression processes were also shown to be increased in spray cases. These thermodynamic features are
shown to change with injection timing and they indicate the potentials of increasing engine thermal efficiency and power density in a direct-injection
spark-ignition gasoline engine.